1. Field of the Invention
This invention relates to amine curable compositions useful in a number of applications particularly flooring and coating applications.
2. Description of the Related Art
A common type of curable composition for use in flooring applications is a curable epoxide composition. Epoxide resins, however, have undesirable attributes such as slow cure rates and high viscosities, especially at low temperatures. Another type of curable composition for use in flooring applications is a curable acrylate composition, however, acrylate systems also demonstrate undesirable attributes, e.g. poor alkaline resistance. The method of polymerization can be a further drawback. Free radical polymerization is inhibited by oxygen and thermally activated polymerization causes problems in some areas, e.g. in flooring applications where it is difficult and problematic to uniformly heat an entire floor for even cure. Ultraviolet cure and electron beam cure are also unsatisfactory for flooring applications since generally one will only get cure on the surface with these systems and, therefore, they are not practical for bulk cure and cure of filled systems.
A combination of the properties imparted by the acrylate and epoxide functionalities is often desirable and curable compositions containing both of these functional groups are known. However, many of these have drawbacks. U.S. Pat. No. 4,051,195 describes curable compositions comprising an epoxide resin which contains more than one 1,2-epoxide group per molecule, a polyacrylate or polymethacrylate ester of a polyol wherein said ester contains more than one terminal acrylate or methacrylate group and an aliphatic amine containing at least three amine hydrogen atoms per molecule of aliphatic amine. Such compositions are described as having enhanced properties relative to an all-epoxy based composition. However, it is well known that amine curing of acrylates occurs much faster than amine curing of epoxides, so that mixtures of epoxy resins and acrylate monomers cure at different rates. This difference in cure rate results in non-homogeneous, two-phase polymers with epoxy rich regions and acrylate rich regions with correspondingly inferior properties including relatively long tack-free times for the cured material, especially at low temperatures, resulting from regions of uncured epoxy.
U.S. Pat. No. 5,198,524 discloses a storage-stable curable adhesive composition comprising a polyacrylate, a polyepoxy resin and a ketimine which undergoes a two-stage cure in which, in a first stage, the adhesive is moisture cured at ambient temperature to provide green strength. In a second stage, the adhesive is post-cured at elevated temperatures to provide a high strength bond. In a preferred embodiment, the epoxy and acrylate functionalities are on the same molecule.
U.S. Pat. No. 4,616,066 provides for a vinyl or acrylic polymer-modified epoxy resin which is the reaction product of (a) an epoxy group-containing vinyl or acrylic polymer with (B) a bisphenol compound and (C) a diglycidyl ether of a bisphenol compound. The vinyl or acrylic polymer-modified epoxy resin is described at column 5, lines 20-23, as being useful in adhesive or coating compositions in combination with known curing agents such as amines. The vinyl and acrylic polymer-modified epoxy resins have no remaining unpolymerized acrylate groups to participate in the curing reaction.
The present invention provides amine-curable compositions which contain materials having both epoxy and acrylate functionalities on the same molecule. These compositions cure rapidly and provide, after amine cure, more homogeneous polymers with correspondingly improved properties.